Marker screw attachment for access opening plugs of underfloor wiring duct



June 3, 1967 DE FOREST D. BUTLER 3,

MARKER SCREW ATTACHMENT FOR ACCESS OPENING PLUGS OF UNDERFLOOR WIRING DUCT Filed NQV. 20, 1963 I NVENTOR.

Z IF @MWM 3 324,612 MARKER SQREW ATTACHMENT FOR ACCESS OPENING PLUGS F UNDERFLOOR WIRING DUCT De Forest D. Butler, Lexington, Ky., assignor to Square D Company, Park Ridge, 111., a corporation of Michigan Filed Nov. 20, 1963, Ser. No. 324,927 7 Claims. (Cl. 52-405) This invention relates generally to underfloor wiring duct and more particularly to plugs and marker screws for the access openings thereof.

In the construction of a building having wiring duct embedded in a concrete floor, it is customary to use wiring duct having equally spaced access openings containing plugs to keep concrete out of the duct when the concrete is poured, each plug being provided with a marker screw so that selected marker screws may be backed off to extend above the level of the concrete and thereby indicate the location of access openings, while other access openings whose screws have not been backed off to extend above the level of the concrete may be located by measuring predetermined distances from visible marker screws. Alternatively, most of the access openings may be provided with plugs having no marker screws.

To provide a marker screw in each plug is expensive and wasteful, since perhaps only one marker screw out of a considerable number need be used. To provide two different kinds of plugs, one kind with marker screws and the other without, is also expensive to a dealer, since two different kinds of plugs must be stocked.

An object of this invention is to provide an improved plug for an access opening of an underfiow wiring duct and a marker screw attachment therefor which may be readily attached thereto at the job site, so that marker screws need not be furnished in each plug and so that only one kind of plug need be furnished with the duct.

Other objects will appear when the following specification is considered along with the acompanying drawings in which:

FIG. 1 is a sectional view of a concrete floor having an underfloor wiring duct embedded therein, the duct being shown in side elevation and having marker screw attachments constructed in accordance with this invention secured to some of the plugs in the access openings thereof;

FIG. 2 is a plan view of a portion of the duct of FIG. 1 with the concrete omitted;

FIG. 3 is an exploded perspective view showing a portion of the duct of FIG. 1 with an access opening, a plug for the opening, and a marker screw attachment therefor;

FIG. 4 is a longitudinal sectional view taken along the line 44 of FIG. 2; and

FIG. 5 is a cross sectional view taken along the line 55 of FIG. 4.

FIG. 1 shows an underfloor wiring duct embedded in a concrete floor 12 and having a plurality of access openings, such as the access opening 13 shown in FIG. 3. The access openings 13 are in an upper wall portion of the duct 10 and are respectively closed by plugs 14 constructed in accordance with the invention, two of the plugs shown being provided respectively with marker screws 16 and each marker screw 16 forming a part of a marker screw attachment constructed in accordance with the invention. Each market screw attachment also includes a marker screw attachment strip 18 (FIGS. 2-5) fully described hereinafter.

The access openings 13 and plugs 14 are substantially complementary in size and shape, the plugs being gen- 3,3 24 ,6 l2 Patented June 13, 1967 erally in the shape of shallow cups designed to fit snugly in the respective openings 13 so as not to fall out but to be readily removable with a hand tool. The plugs are provided respectively with peripheral flange portions 20 for engagement with respective upstanding collar portions 22 provided on the duct 10 around the openings 13. In plan View the openings 13 and plugs 14 are elongated longitudinally of the duct and have rounded opposite end portions.

In accordance with the invention, the bottom and side wall portions of each plug 14 are formed to provide supporting wall portions and marker screw attachment strip expansion accommodating wall portions on opposite sides of the plug for cooperation with one of the marker screw attachment strips 18. Thus, two opposed pairs of indentations 24 (FIGURES 3 and 4) are provided in each plug. The upper indentations 24 in each plug might be considered to be in opposed side wall portions thereof and the lower indentations 24 in each plug might be considered to be in the bottom wall portion thereof, it being understood that in the vinicity of the indentations there is no clear division between the bottom wall portion and the side wall portions of the plug. The indentations 24 in each plug provide or result in an opposed pair of expansion accommodating wall portion 26 extending generally vertically in FIG. 5 and spaced from the respective collar portion 22 of the duct, and a pair of supporting wall portions 28 extending horizontally in FIG. 5 and joined to the wall portion 26.

The marker screw attachment strips 18 are formed from flat elongated pieces of metal, each of the opposite end portions of each piece being provided with a pair of spaced, sharply pointed tooth portions 30 and the center portion of each piece being extruded to form a hole for mounting one of the marker screws 16, the extruded metal 32 (FIGS. 4 and 5) providing additional thread bearing area. The pieces are longitudinally flatwise curved into an arcuate shape, as best shown in FIG. 5, to complete the manufacture of the marker screw attachment strips 18.

Before the concrete floor 12 is poured, the access openings 13 of the duct 1t! are respectively plugged with identical plugs 14. Marker screw attachment strips 18, each having a marker screw 16 mounted therein, are then attached to the plugs 14 of selected access openings. The strips 18 having screws 16 mounted respectively therein are attached by merely placing them in position on the supporting wall portions 28 of the respective plugs 14 and pounding on the screws 16 with a tool such as a hammer. A single hammer blow on a screw 16 will cause the tooth portions 30 of the respective strip 18 to deform or pierce the walls of the respective plug 14 and will also flatten the respective strip 18 slightly from its original curved shape, as will be understood, and thus elongate it somewhat so that it cannot be readily lifted from the respective plug 14 due to the cooperative engagement of the tooth portions 30 therewith. The spacing of the expansion accommodating wall portions 26 from the relatively rigid collar portion 22 of the duct accommodates the elongation of the strip 18. After the strips 18 are attached to selected plugs 14, the marker screws 16 therein are backed off to extend above the intended level of the concrete and thus indicate the location of the selected access openings 13 after the concrete is poured.

It will thus be seen that marker screws do not have to be provided for every access opening in the duct, and that it is not necessary for a dealer to stock two kinds of plugs, one with marker screws and one without, since the marker screw attachments may be readily secured to all or selected ones of the plugs at the job site.

1. An underfloor wiring duct having an access opening disposed in an upper wall portion thereof and defined by an upstanding collar portion of said duct, a plug disposed in said access opening, said plug being generally in the form of a shallow flanged cup and fitting snugly in said access opening but having a pair of expansion accommodating wall portions respectively disposed on opposed sides thereof in space relationship to said upstanding collar portion of said duct, each of said expansion accommodating wall portions having a deformation therein extending toward said upstanding collar portion from inside said cup and an elongated longitudinally flatwise curved marker screw attachment strip having a marker screw threadedly mounted therein and extending therethrough, said marker screw attachment strip being disposed in said plug with the concave side thereof toward said plug and with opposite end portions thereof disposed adjacent said expansion accommodating wall portions of said plug and having a pair of tooth portions respectively disposed adjacent opposite ends thereof and received in said deformations to secure said strip to said plug.

2. The combination claimed in claim 1, wherein each of the opposite end portions of said marker screw attachment strip is provided with a pair of spaced tooth portions and each of said expansion accommodating wall portions of said plug has a pair of spaced deformations in which the respective pair of tooth portions of said strip are received.

3. The combination claimed in claim 1, wherein said marker screw attachment strip is provided with a hole for receiving said marker screw and is extruded around said hole to provide additional thread bearing area for said screw.

4. A marker screw attachment comprising an elongated longitudinally flatwise curved marker screw attachment strip deformable in the securing thereof to a plug for an access opening of an underfloor wiring duct, and a marker screw threadedly mounted in said strip and extending therethrough centrally thereof, each of the opposite end portions of said strip having a tooth portion for securing said strip to said plug.

5. A marker screw attachment as claimed in claim 4, wherein each of the opposite end portions of said strip is provided with a pair of spaced tooth portions for securing said strip to said plug.

6. The combination claimed in claim 4, wherein said marker screw attachment strip is provided with a hole for receiving said marker screw and is extruded around said hole to provide additional thread bearing area for said screw.

7. A method of mounting a marker screw in a generally cup-shaped plug disposed in an upstanding collar portion defining an access opening of an underfloor wiring duct, the plug having an opposed pair of generally vertically extending expansion accommodating wall portions laterally spaced from said collar portion and an opposed pair of generally horizontally extending wall portions respectively adjacent said vertically extending wall portions, said method comprising providing an elongated rnarker screw attachment strip, providing a threaded hole through a central portion of said strip, forming said strip into a longitudinally and flatwise curved generally arcuate shape, providing a marker screw, assembling said marker screw with said strip by turning said screw into said threaded hole from an outer side of the curved strip, placing the screw and strip assembly in said plug with an inner side of the curved strip facing the plug and with opposite end portions of the strip in engagement respectively with said horizonally extending wall portions, and deforming said strip and said vertically extending wall portions by means of a blow with a tool such as a hammer to secure said opposite end portions respectively to said vertically extending wall portions.

References Cited UNITED STATES PATENTS 801,683 10/1905 Penfold 22024.5 1,758,989 5/1930 Walker 52221 1,884,424 10/1932 Walker 52221 2,214,732 9/1940 Kraft 220-245 2,297,179 9/1942 Walker 5222l 2,775,812 1/1957 Mohr 29-407 3,166,631 1/1965 Reiland 5222 0 FOREIGN PATENTS 1,047,449 7/ 1953 France.

FRANK L. ABBOTT, Primary Examiner.

J. L. RIDGILL, Assistant Examiner. 

1. AN UNDERFLOOR WIRING DUCT HAVING AN ACCESS OPENING DISPOSED IN AN UPPER WALL PORTION THEREOF AND DEDINED BY AN UPATANDING COLLAR PORTION OF SAID DUCT, A PLUG DISPOSED IN SAID ACCESS OPENING, SAID PLUG BEING GENERALLY IN THE FORM OF A SHALLOW FLANGED CUP AND FITTING SNUGLY IN SAID ACCESS OPENING BUT HAVING A PAIR OF EXPANSION ACCOMMODATING WALL PORTIONS RESPECTIVELY DISPOSED ON OPPOSED SIDES THEREOF IN SPACE RELATIONSHIP TO SAID UPSTANDING COLLAR PORTION OF SAID DUCT, EACH OF SAID EXPANSION ACCOMMODATING WALL PORTIONS HAVING A DEFORMATION THEREIN EXTENDING TOWARDS SAID UPSTANDING COLLAR PORTION FROM INSIDE SAID CUP AND AN ELONGATED LONGITUDINALLY FLATWISE CURVED MARKER SCREW ATTACHMENT STRIP HAVING A 